Pharmaceuticals have become important emerging contaminants, due to their presence in environmental waters (following incomplete removal in wastewater treatment or diffuse-source contamination), threat to drinking water, and concern about possible estrogenic and other adverse effects, both to wildlife and humans. A major concern for pharmaceuticals also includes the development of bacterial resistance (creation of “Super Bugs”) from the release of antibiotics to the environment, and there are also concerns that antibiotics will decrease biodegradation of leaf and other plant materials, which serves as the primary food source for aquatic life in rivers and streams. It is estimated that approximately 3000 different substances are used as pharmaceutical ingredients, including painkillers, antibiotics, antidiabetics, betablockers, contraceptives, lipid regulators, antidepressants, and impotence drugs. Pharmaceuticals are introduced not only by humans but also through veterinary use for livestock, poultry, and fish farming, as various drugs are commonly given to farm animals to prevent illness and disease and to increase the size of the animals.
Metal-organic frameworks (MOFs), which are crystalline porous materials constructed from multifunctional ligands and metal ions, have drawn considerable attention for environmental remediation purposes owing to their high porosity and tenability. Particularly, most studies concerning adsorption have investigated dyes, organoarsenic, phenols, and heavy metal removal using MOFs nanoparticle from the liquid phase, with the large adsorption capacity and fast adsorption kinetics. However, the use of MOFs nanoparticle is heavily restricted due to their poor separability because significant post-treatment filtration or centrifuge is required to remove the MOFs from the purified water, and obvious loss of adsorbents is quite possible to happen during such processes. To overcome the shortcoming, immobilization of active micro- or nanoscale particle appears to provide an approach.
Natural polymers have been long favored due to their additional advantages of being inexpensive, plentiful, non-toxic, and renewable, such as sodium alginate and chitosan, which can be easily formulated into a few millimeters beads easily separated from a liquid medium. The flexibility of nano-particles incorporation into sodium alginate and chitosan are considered to be an excellent way to immobilize active micro- or nanoscale particles and present novel composite adsorbents. Among over 10,000 MOF materials, there are several transition-metal-based MOFs that are stable under liquid phase reaction conditions. These include mesoporous chromium(III) terephthalate (MIL-101), . . . . Due to the high stability, these MOFs exhibits no detectable leaching of metal ions into solutions, allowing its safe use in different applications. In addition, these MOFs possess high densities of transition metal ions with Lewis acid properties, which can be stable under acid conditions. The resulting composite materials are effective removal for pharmaceuticals.